Boil potatoes and carrots in their skins until tender. Cool, peel off the skin and cut into small cubes. Peel the onion and cut into thin quarter rings. Drain the green peas. Clean the fish from bones and skin. Divide the mackerel pulp into small pieces. Peel and seed the apple and cut into small cubes. Hard-boil the egg, cool and peel off the shell. Grate the egg on a coarse grater. Cut a circle out of black bread. Fry it on both sides in a dry frying pan.
Combine chopped potatoes and carrots in a deep bowl. Add onions, green peas, mackerel pulp and chopped apple to them. Salt the salad to taste and season with mayonnaise. Mix everything well.
Using a mold, place the salad on toasted black bread. Place a heap of grated egg on top. Garnish with a parsley leaf. It can also be served in a common salad bowl.